Field effect transistors (FETs) are the basic building block of today's integrated circuits (ICs). Such transistors can be formed in conventional substrates (such as silicon) or in silicon-on-insulator (SOI) substrates. State of the art MOS transistors are fabricated by depositing a gate stack material over a gate dielectric and a substrate. Generally, the MOS transistor fabrication process implements lithography and etching processes to define the conductive, e.g., poly silicon (poly Si), Si, gate structures. Source/drain extensions are formed by implantation, in which the implant is performed using a spacer to create a specific distance between the gate and the implanted junction. In some instances, such as in the manufacture of an NFET device, the source/drain extensions for the NFET device are implanted with no spacer. For a PFET device, the source/drain extensions are typically implanted with a spacer present. A thicker spacer is typically formed after the source/drain extensions have been implanted. Deep source/drain implants are then performed with the thick spacer present. High temperature anneals are performed to activate the junctions after which the source and drain regions and the top portion of the gate are silicided. Silicide formation typically requires that a refractory metal be deposited on the silicon wafer followed by a high temperature thermal anneal process to produce the silicide material. The structure is then passivated by a blanket-deposited conformal dielectric material.
In order to be able to make ICs, such as memory, logic, and other devices, of higher integration density than currently feasible, one has to find a way to further downscale the dimensions of field effect transistors (FETs), such as metal oxide semiconductors. The downscaling of transistor dimensions allows for improved performance as well as compactness, but such downscaling has some device degrading effects.
Further scaling of semiconducting devices requires that the electrical leakage and contamination transfer pathways through seams present in a conventional spacers be interrupted to ensure that the electrical pathways and contaminant transfer pathways between the gate conductor and the contacts to the source and drain region of the device be severed.